The Vaccine Branch FACS (Flow Cytometry) Core Facility has been created to meet an unmet need on the Bethesda Campus of NCI for a Flow Cytometry Core Facility with BL2/BL3 containment necessary to safely sort live cells infected with retroviruses, such as HIV/SIV, and other infectious agents known or suspected in blood and tissue samples. The facility has a multicolor cell sorter currently in use for standard and infectious sorting. In addition, this facility has analysis capabilities from five multicolor flow cytometry instruments that were donated to the facility from three Investigators in the CCR, and through IATAP funding. Laboratory space renovations were completed in May 2008, and the donated flow cytometers were relocated to the facility in June 2008. The facility purchased a 4 laser high end analyzer and a 3 laser high speed cell sorter. These were purchased at the beginning of FY09 and installed in Q2 FY09. The facility purchase a 28-color BD FACSymphony A5 in 2016. A new 28-color FACSymphony A5 is being purchase to replace a discontinued 12-color BD LSRII flow cytometer. The facility currently maintains one investigator-run 2 laser 4 color analog flow cytometer, two investigator-run 4 laser 18 color high end digital flow cytometers, two investigator run 5 laser 28 color high end digital flow cytometers (one is currently being purchased for installation in FY2019).The facility also has two cell sorters: a 4 laser 16 color digital cell sorter equipped with containment for use as an infectious cell sorter and a 5 laser 19 color cell sorter in a biological safety cabinet. The facility currently supports more than 70 NCI/CCR Investigators from the Vaccine Branch, the Laboratory of Receptor Biology and Gene Expression, the Laboratory of Cellular Oncology, and the Laboratory of Cancer Biology and Genetics and Pediatric Oncology Branch. In addition to NCI investigators, the Facility Manager is working on a collaboration with an investigator from NEI and NIAID. Experiments currently conducted in the facility involve multi-parameter single cell analysis of cells from human, non-human primate and mouse primary sources. Additionally analysis is also conducted on in vitro cultured cells. Reagents for these experiments include monoclonal and polyclonal antibodies with fluorescent labels and fluorescent dyes used for staining a variety of cellular components. Current applications being supported by the facility include multi-color phenotypic analysis, cell cycle analysis, apoptosis analysis, proliferation analysis with BrdU and CFSE, intracellular cytokine analysis, rare event analysis and calcium flux analysis. Currently supported projects include, but are not limited to, immune monitoring for HIV, SIV, HTLV-1 and HTLV-2 vaccine studies on non-human primates, and monitoring the results of gene expression on cell proliferation and apoptosis.